Serguei Primak

A Novel MIMO-Aware Distributed Media Access Control Scheme for IEEE 802.11 Wireless Local Area Networks

The current Internet architecture allows malicious nodes to disguise their origin during denial-of-service attacks with IP spoofing. A well-known solution to identify these nodes is IP traceback. In this paper, we introduce and analyze a lightweight single-packet IP traceback system that does not store any data in the network core. The proposed system relies on a novel data structure called Generalized Bloom Filter, which is tamper resistant. In addition, an efficient improved path reconstruction procedure is introduced and evaluated. Analytical and simulation results are presented to show the effectiveness of the proposed scheme. The simulations are performed in an Internet-based scenario and the results show that the proposed system locates the real attack path with high accuracy.This paper proposes a new distributed media access control (MAC) scheme to improve the network performance of Multiple-Input Multiple-Output (MIMO) wireless systems. In particular, this novel MAC scheme efficiently schedules two simultaneous transmissions between wireless stations (each equipped with three antennas) that are located in a single collision domain. Along with weighted nulling and intelligent packet fragmentation, this MAC scheme is capable of providing more efficient utilization of channel resources. The proposed MIMO-aware MAC scheme is compatible with the IEEE 802.11 standard. Detailed simulations are carried out to study the performance of the proposed scheme. The performance of the MIMO-aware MAC scheme is also compared with a recently proposed MIMO MAC scheme in the literature which is compatible with the IEEE 802.11 standard. Comparisons reveal that the proposed MIMO-aware MAC scheme achieves better throughput and delay performance under both saturated and unsaturated conditions.

Channel estimation using DPSS based frames

Accurate and sparse representation of a moderately fast fading channel using bases functions is achievable when both channel and bases bands align. If a mismatch exists, usually a larger number of bases functions is needed to achieve the same accuracy. In this paper, we propose a novel approach for channel estimation based on frames, which preserves sparsity and improves estimation accuracy. Members of the frame are formed by modulating and varying the bandwidth of discrete prolate spheroidal sequences (DPSS) in order to reflect various scattering scenarios. To achieve the sparsity of the proposed representation, a matching pursuit approach is employed. The estimation accuracy of the scheme is evaluated and compared with the accuracy of a Slepian basis expansion estimator based on DPSS for a variety of mobile channel parameters. The results clearly indicate that for the same number of atoms, a significantly higher estimation accuracy is achievable with the proposed scheme when compared to the DPSS estimator.

Effects of latency on telesurgery: an experimental study

The paper is concerned with determining the feasibility of performing telesurgery over long communication links. It describes an experimental testbed for telesurgery that is currently available in our laboratory. The tesbed is capable of supporting both wired and satellite connections as well as simulated network environments. The feasibility of performing telesurgery over a satellite link with approximately 600 ms delay is shown through a number of dry and wet lab experiments. Quantative results of these experiments are also discussed.

A two dimensional quantization algorithm for CIR-based physical layer authentication

Recently, channel impulse response (CIR) based physical layer authentication has been studied to enhance the security of wireless communications. However, the reliability of CIR-based authentication is substantially reduced at low signal-to-noise ratio (SNR) conditions due to the presence of communications noise, channel estimation error and mobility induced channel variation. To this end, we integrate additional multipath delay characteristics into the CIR-based physical layer authentication and propose a two dimensional quantization scheme to tolerate these random errors of CIRs for reduced false alarm rate and more reliable spoofing detection. Instead of directly comparing the estimated CIRs from different transmitters for authentication purpose, we first quantize the CIR estimates in two dimensions (i.e., the amplitude dimension and multipath delay dimension) and then differentiate transmitters based on the quantizer outputs with a binary hypothesis testing. More specifically, the quantization intervals are determined by using a searching algorithm based on a guaranteed miss probability of detection of the presence of spoofing attack. A logarithmic likelihood ratio test (LLRT) is used to evaluate the authentication performance, and a threshold with a constant value is used for the decision-making of authentication under the binary hypothesis testing. To verify the effectiveness of proposed algorithm, an orthogonal frequency division multiplexing (OFDM) system is considered in our simulation.

Ubiquitous WBAN-based Electrocardiogram monitoring system

This paper presents a remote patient monitoring system within the scope of Body Area Network standardization. In this regime, wireless sensor networks are used to continuously acquire the patients Electrocardiogram signs and transmit data to the base station via IEEE.802.15. The personal Server (PS) which is responsible to provide real-time displaying, storing, and analyzing the patients vital signs is developed in MATLAB. It also transfers ECG streams in real-time to a remote client such as a physician or medical center through internet. The PS has the potential to be integrated with home or hospital computer systems. A prototype of this system has been developed and implemented. The developed system takes advantage of two important features for healthcare monitoring: (i) ECG data acquisition using wearable sensors and (ii) real-time data remote through internet. The fact that our system is interacting with sensor network nodes using MATLAB makes it distinct from other previous works.

On Achievable Data Rates and Optimal Power Allocation in Fading Channels with Imperfect Channel State Information

Achievable rates of wireless communication systems with pilot-based channel estimation are investigated for the case of time-selective fading. Novel analytical expressions for the maximum achievable rates of such systems are derived in terms of the system signal-to-noise ratio (SNR), fading rate and estimation scheme deployed. The frame size is optimized jointly based on the SNR and the fading rate. The maximum rate achieving coding scheme is suggested and shown to be a modified version of the classical water-filling algorithm that accounts for imperfect channel state information (CSI) at the transmitter. The impact of the estimation scheme and the angular spread of the received signal on the quality of estimation and achievable rates is evaluated. A number of numerical simulations are provided to illustrate the dependence of the optimal block length and achievable rates on SNR, fading rate, estimation scheme and angular spread of the channel.

On the Second Order Statistics of Generalized Gamma Process

The second order statistics, such as the level crossing rate and the average fade duration of a generalized Gamma distribution are derived in this paper. Joint distribution of the process and its derivative and the marginal distribution of the derivative is developed. It is shown that apart from the Nakagami case the velocity of the process is dependent on the value of the process. The results are applied to derive some characteristics of error flow in channels with dual mobility, generalized Gamma fading and basic modulations

Effects of Side Information on Complexity Reduction in Superimposed Pilot Channel Estimation in OFDM Systems

A novel, reduced complexity iterative channel estimation algorithm for OFDM systems using superimposed pilots is proposed. It utilizes past channel estimations of double correlated channel as a side information to reduce number of iterations. Since pilots are available at all positions of the time-frequency OFDM grid in superimposed technique, the performance of the channel estimation does not degrade because of the variations of the fast fading channel between two pilots. On the other hand since no subcarrier is reserved for channel estimation purpose, superimposed pilot technique leads to improved spectral efficiency comparing to in-band OFDM pilots. However interference from data carrying signals made channel estimation more complex. In this paper, Least Square (LS) channel estimation followed by two dimensional Wiener filter for reducing OFDM symbol interference is done iteratively to achieve the Minimum Mean Square Error (MMSE). Small variations of the channel over each OFDM symbol duration are neglected due to a high data rate, but the values between different OFDM symbols are assumed correlated. The channel is modeled as a double selective, i.e. both frequency selectivity channel and Doppler shift are taken into consideration. Past channel estimates are used as side information for the present channel estimation to improve the forthcoming channel estimation at the first iteration and reduce the total number of iterations required.

Secret Key Generation Using Physical Channels with Imperfect CSI

Providing extra security in wireless communication networks using channel impulse response as a source of common randomness is an appealing direction in prospective systems. While some theoretical and experimental work has demonstrated its potential, a number of issues remain unexplored. This paper is concerned with the reliability of secret key generation under practical estimation requirements. We provide an analytical expression which relates the channel SNRs and degree of reciprocity to probability of key mismatch. In the next step we show how this affects key reconciliation and secrecy leaking. Finally, we consider how quantization with a protective band can help to trade the secret key rate for increased reliability and security of the scheme.

Performance Analysis of M-Ary PSK Modulation Schemes over Multiple Double Rayleigh Fading Channels with EGC in Cooperative Networks

This article studies the performance of M-ary phase shift keying (PSK) modulation schemes over mobile-to-mobile (M2M) fading channels with equal gain combining (EGC) in cooperative networks. The frequency-nonselective M2M fading channels are modeled assuming non-line-of-sight (NLOS) propagation conditions. Furthermore, a dual-hop amplify-and-forward relay type cooperative network is taken into consideration here. It is assumed that K diversity branches are present between the source mobile station and the destination mobile station via K mobile relays. The performance of M-ary PSK modulation schemes is analyzed by evaluating the average bit error probability (BEP). We have derived a simple analytical approximation for the average BEP of M-ary PSK modulation schemes over relay-based M2M fading channels with EGC. The validity and accuracy of the analytical approximation is confirmed by simulations. The presented results show that in a dual-hop relay system with EGC, there is a remarkable improvement in the diversity gain as the number of diversity branches K increases.